Extant research on open source software (OSS) has primarily focused on software developers and active users but has paid limited attention to the less visible ?passive? users who form the silent majority of OSS communities. Passive users play a critical role in the adoption and diffusion of OSS, and we need more research to understand their behaviors and motivations. We address this gap by drawing on the sociological theory of community markers. The three community markers in the context of OSS are loyalty, ideology, and identification. We also draw on marketing literature to propose four contributory behaviors of passive users of OSS that we theorize to be impacted by the community markers: user brand-extension, word-of-mouth, endorsement, and community involvement. We further classify passive users? contributory behaviors according to the difficulty of their enactment and examine the differential influence of the OSS community markers. Partial-least squares (PLS) analyses of data obtained through a survey of passive users of an OSS product provide support for the majority of the hypotheses.